Getting window previews

Matthew Brush mbrush at
Sat Jul 18 01:48:20 CEST 2015

On 15-07-17 02:09 PM, adlo wrote:
> What functions does skippy-xd use to get the previews?

I have no idea what that is.

> [...]
> What functions does xfwm4 use?

I have no idea, I would guess XGetImage or something else depending on X 
extensions maybe. There was a thread about it on this mailing list a 
while back (search for "Window previews in xfwm4"), maybe it gives some 

> How CPU-efficient is XGetImage (or XShmGetImage) compared to the other two methods? Which method is the most CPU-efficient?

I don't know what the other two methods are but I would guess they're 
"efficient enough". If you got everything working and after 
using/profiling found too slow, then you could look to more advanced 
ways. I've used XGetImage before on dual-screen root window, showing a 
preview in a widget at ~30fps and it was "fast enough" for my use.

> Do you know any details about the methods I could use to convert the image to a GdkPixbuf?

If it's for preview you probably don't need GdkPixbuf as you can convert 
straight from an XImage to a Cairo image surface and paint it  onto a 
widget. There's probably tricks to avoid extra copying too, I'm no 
expert on Xlib stuff.

Matthew Brush

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